The present invention relates to a fuel supply system for a vehicle, in particular, it relates to a fuel supply system for a vehicle which can be favorably employed to supply fuel inside a fuel tank to a vehicle engine.
Generally, a fuel supply system which supplies fuel to an engine or similar device comprises a pump unit which delivers fuel to the engine, and a fuel level detection device which detects a level of fuel remaining in a fuel tank, both the pump unit and the fuel level detection device being disposed inside the fuel tank. The pump unit comprises a fuel pump installed on an upper surface of the fuel tank to suck fuel and deliver the fuel, and a chamber which is cylindrical and closed at the bottom to maintain an amount of fuel around an intake opening of the fuel pump.
The fuel level detection device is mostly comprised of a float which floats on the surface of fuel stored inside the fuel tank, and thus has an upward or downward displacement corresponding to a rise or fall of the surface of the fuel, and a sensor member which is installed on the pump unit to detect a vertical position or height of the surface of the fuel, i.e., a level of the fuel, by detecting a vertical position or height of the float.
Japanese Patent Provisional Application (Helsei) 10-47185 discloses a fuel supply system for supplying fuel that has been sucked by the fuel pump to fuel injectors of an engine by driving the fuel pump of the pump unit.
The float, which floats on the surface of the fuel held in the fuel tank, has a vertical displacement according to a change in height of the surface of the fuel, and the amount of fuel remaining in the fuel tank is detected by detecting the position of the float with the sensor member of the fuel level detection device.
However, in a fuel supply system according to the above related art, the sensor member of the fuel level detection device is installed on the pump unit, and the pump unit is installed on the upper surface of the fuel tank.
Depending on manufacturing tolerances during assembly, the distance or height from the inside bottom to the inside top of the fuel tank differs slightly with individual fuel tanks. Also, a fuel tank expands or contracts depending on internal pressure of the fuel tank, and the vertical distance from the inside bottom to the inside top of the fuel tank changes.
There is a recent trend to form fuel tanks using a flexible, light-weight material such as synthetic resin in striving for lightness of the entire vehicle, and a fuel tank designed using flexible material deforms depending on a range of factors including change in volume and therefore weight of fuel being held in the tank, change in pressure within the fuel tank, change in temperature around the exterior of the fuel tank, or vibration or shock while the vehicle is traveling.
When a fuel tank deforms in such a way, the surface of the fuel inside the fuel tank rises or falls correspondingly with no change in the actual amount of fuel remaining. Thus, a fuel level detection device according to the related art, which is installed on an upper surface of a fuel tank to detect the amount of fuel remaining by detecting the height or level of the surface of the fuel under such conditions, gives a detection result that is not an accurate indication of the amount of fuel remaining. The problem that arises, then, is how to stabilize a remaining amount of fuel relative to a fuel level detection device to obtain an accurate detection result.
It is therefore an object of the present invention to provide a fuel supply system which is capable of stabilizing fuel inside a fuel tank relative to a fuel level detection device so that the level of remaining fuel can be more accurately determined.
An aspect of the present invention resides in a fuel supply system for a vehicle, the fuel supply system comprising a fuel tank, a pump unit which is installed on a top of the fuel tank, the pump unit sucking fuel from the fuel tank and delivering the fuel to an engine, a fuel level detection device disposed in the fuel tank, the fuel level detection device comprising a float which floats on the fuel in the fuel tank, and a sensor member which is disposed between an inside bottom of the fuel tank and the pump unit, the sensor member detecting a displacement of the float, and a pressing member which is disposed between the pump unit and the sensor member, the pressing member tending to expand and press against the sensor member, the sensor member being pressed against the inside bottom of the fuel tank.
Another aspect of the present invention resides in a fuel supply system for a vehicle which comprises an engine, the fuel supply system comprising a fuel tank, pump means for sucking fuel from the fuel tank and delivering the fuel to the engine, the pump means comprising containing means for maintaining an amount of fuel inside the pump means, the containing means being disposed inside the fuel tank, a float which floats on the surface of fuel in the fuel tank, the float having an upward or downward displacement which corresponds to a respective rise or fall in the surface of the fuel, sensor means for detecting the displacement of the float, the sensor means being disposed on a bottom of the fuel tank, and pressing means for pressing the sensor member against the bottom of the fuel tank with elasticity, the pressing means extending from the containing means.
A further aspect of the present invention resides in a fuel supply system for a vehicle comprising an engine and a fuel tank, the fuel supply system comprising a pump unit which is disposed on a top of the fuel tank, the pump unit comprising a chamber suspended inside the fuel tank, a sensor member which is disposed on an inside bottom of the fuel tank, a float which has a displacement corresponding to a change in a level of the surface of the fuel, the displacement being detected by the sensor member, and elastic pressing means for pressing against the sensor member with elasticity, the elastic pressing means being disposed between a top of the sensor member and the chamber.